Synthesis and Magnetic Properties of Water-Based Fe3O4 Ferrofluid

Abstract:

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Stable water-based Fe3O4 ferrofluid was obtained by three steps. Fe3O4 nanoparticles with the size of about 10 nm were first prepared by chemical co-deposition method. In order to prevent Fe3O4 nanoparticles from agglomerating, they were coated by bilayer surfactants. Then, the coated Fe3O4 nanoparticles were dispersed well into water. Due to the actions of electrostatic force and hydrogen bond, the water-based Fe3O4 ferrofluids can keep stable for two years and no layered phenomenon occurred. The ferrofluid has high saturation magnetization, low remnant magnetization and coercive force.

Abstract: BiFeO3 powders were prepared by sol-gel process and calcined at different temperatures. The DTA curve shows an obvious exothermic peak near 480.5°C, the temperature close to BiFeO3 formation temperature, which is agreement with the XRD results (450°C). After calcining at 600°C for 1h, XRD spectra has the emergence of several sharp diffraction peaks, compared with the standard XRD spectrum of the crystal BiFeO3. As the calcining temperature increased, the diffraction peak intensity of the XRD spectra of BiFeO3 gradually increased and the diffraction peaks became sharply, indicating that the grain size gradually became larger. There is a clear endothermic peak near 825.1°C, which is the α phase to β phase transition from the knowledge of the phase diagram and in good agreement with the reported Curie temperature.

Abstract: Two different bidisperse approximations of one gamma-distribution were examined in the present manuscript. The bidisperse system was chosen as the first step to allow for polydispersity when studying thermodynamics and microstructure of magnetic fluids. The author used the first-order modified mean-field model for investigating magnetization curves for these approximations and showed that curves are almost identical. Also analyzed was the influence of choosing variant of constructed bidisperse model on the structure factors, which were constructed using the mathematical model, developed in the paper by Novak et al. [J.Chem.Phys. 139 (2013) 224905].

Abstract: In this study, Iron Oxide (Fe3O4) nanoparticles water based ferrofluid, was synthesized by co-precipitation method. XRD was used to study the structural characterization of the sample and to measure the size of the crystallites (using Scherrer equation). TEM was utilized to examine the shape, the size distribution and the morphology of the nanoparticles. VSM was carried out to measure the magnetic properties (like Mr, Ms and Hc) of the Fe3O4 (magnetite) nanoparticle and magnetite ferrofluid at 80 and 300 K. The results indicate that the average size of the magnetite roughly spherical shape nanoparticles is 13nm. The VSM results show that the magnetite ferrofluid contains single domain magnetic nanoparticles with superparamagnetic behavior. In addition, the magnetic measurements demonstrate that with decreasing the temperature of the ferrofluid, its magnetic softness decreases while its anisotropy increases.